Human hair is exposed to highly-diverse environmental influences over a prolonged period—in the case of long hair, even over several years. These environmental influences can damage and destabilize the hair fibers. Cosmetic treatments such as permanent waves, oxidative coloring and event treatments during which the hair is exposed to elevated temperatures (e.g. the use of hair straighteners) can also severely damage the hair. All these influences and treatments cause destructive changes to the hair structure, and these can culminate in impaired combability of dry and wet hair, less shine and reduced softness.
There is therefore a need to further improve hair treatment products and find active ingredients which stabilize the structure of the keratin fibers.
In the prior art, keratin cross-linkers are often used to achieve structural stabilization of the hair structure. Keratin cross-linkers are unsaturated, monomeric compounds with a molecular mass of less than about 500 g/mol. When keratin cross-linkers are applied to hair, they are able to diffuse well into the hair fiber due to their small molecular mass. Inside the hair fiber, the keratin cross-linkers then form—either with the hair fiber itself or with other cross-linker molecules—adducts, said adduct formation occurring at the double bond of each cross-linker molecule.
Corresponding keratin cross-linkers are described, for example, in EP 2478892 A1. In chemical terms, this cross-linking is effectively the addition to a double bond. In order to activate the double bond of the keratin cross-linker, this is often located in close proximity of a group with strong electron-withdrawing properties (a carboxyl group, for example). The addition reaction can also be further facilitated by the use of initiators. In EP 2478892 A1, persulfates, peracids or azo compounds, for example, can also be used. In this context, an acid range of from about 4.0 to about 6.9 is described as the optimum pH value for this reaction.
In the studies on which this application is based, however, it has now been found that the keratin cross-linkers described in EP 2478892 A1 are not optimally adapted to the bleaching of keratin fibers.
The present disclosure therefore addresses the problem of providing an agent to stabilize keratin fibers, more particularly human hair. The active substances used in this agent should have a stabilizing effect particularly on the inner structure of the keratin fibers. Moreover, the active substances used in the agent ought to be compatible with a large number of cosmetic treatment procedures (such as bleaching agents, permanent wave agents, etc.).